1. Field of the Invention
The invention is related to a device for modifying the pressure distribution of a ski, such as an alpine ski, along its sliding surface.
2. Description of Background and Material Information
Skis that are used for alpine skiing are constituted by relatively long boards, on which the boots of the skier are retained, most often by binding elements. The boots and the binding elements are located approximately in the median zone of the ski, commonly called the middle sole.
In the resting position, skis themselves have a natural arch; moreover, they have a certain flexibility. During skiing, the ski is deformed elastically to react to the various biases to which it is subject from the skier, and by reaction, from the surface on which it slides.
The main force to which the ski is subjected, originating from the skier, is generated by the weight of the skier. This weight is localized approximately in the middle sole zone of the ski.
The ski is also subject to biases by the binding elements. In fact, it is known that the binding elements pinch the boot. To do this, the rear binding element is generally slidably mounted, and it is returned elastically frontwardly by springs that are called return springs. The reaction to this pinching action is transmitted by the binding elements to the ski. This reaction is however different, depending on whether the front binding element or the rear binding element are each affixed to the ski, or whether the front binding element is affixed to the ski and the rear binding element is connected to the front binding element by a non-stretchable means, such as a blade or plate.
The ski is also influenced by the position of the skier, and whether the skier carries his or her weight at the front or at the rear of the skis.
It is known that the behavior of the ski and especially its movement on snow can be modified by influencing its arch, or by the longitudinal distribution of the ski on the snow. By playing with this pressure distribution, it is known that the characteristics of the ski can be modified to favor turning, or to favor gliding. That is, a ski's ability to turn easily or to have great stability during movement can be facilitated.
For skis that are currently on the market, pressure distribution of the ski on the snow is basically determined by the internal structure of the ski, and by the mode of assembly of the binding elements to the ski, that is, with or without a connection blade between the front and rear elements. The distribution of pressure can also be influenced by the intensity of thrust provided to the return spring.
Devices are known with an attached element that enable the pressure distribution of the ski on the snow to be modified. Thus, the European Patent Application 183,586 describes a blade made of an elastic material attached on top of the ski, between the binding elements and the ski. This blade has cursors in the area of its front end and its rear end, whereby a portion of the forces to which the ski is subjected is transmitted vertically. This device, however, has the disadvantage of providing only a modest performance at the cost of being substantially cumbersome. It is adapted for cases where both feet of the skier are in support on the same ski, to avoid the entire weight of the skier from being concentrated in the middle sole zone. It would be ill-adapted to a pair of traditional skis.
In European Patent Application No. 409,749 a device is disclosed that is constituted by a plate that is raised with respect to the upper surface of the ski, maintained between two longitudinal abutments. Elastic shock absorption means are positioned between the plate and the abutments, and the pre-stress exerted on the elastic means is adjustable. The bindings are mounted on the plate. This device gives good results, but its disadvantage is that the plate is raised with respect to the ski along its entire length. It thus behaves like a stiffener of the ski and, due to this fact, it disturbs the flexional movements of the ski. Moreover, the plate induces an identical pre-stress towards the front and towards the rear of the plate on the ski.
It must also be noted that these known devices induce a static type of modification of the pressure distribution on the ski, i.e., this induced modification is not influenced by the position of the skier on the skis during sliding.